Design of four-ordered cross-coupled bandpass filters with low-temperature co-fired ceramic technology

A new method to realise the four-ordered quasi-elliptic bandpass filters with low-temperature co-fired ceramic technology has been proposed; in particular, the semi-lumped structure is employed. With the assistance of the non-adjacent cross coupling, a pair of transmission zeros can be generated on both sides of the passband skirt. Moreover, with the coupling between the source and load ports, an extra pair of transmission zeros will be generated so that there will be greater outband suppression on both sides of the passband skirt. The analysis and design procedures are provided. In addition, the match between the electromagnetic simulation and results of measurement validates the proposed structures.